The invention relates to a dishwasher with a sorption drier. The invention also relates to a method for operating a dishwasher with at least one partial programme step with rinsing liquor that is to be heated to a nominal temperature, e.g. “Clean”, wherein air that is heated in this partial programme step by a heating device and is used for desorption of a reversibly dehydratable material and/or ambient air is conducted from a rinsing container of the dishwasher by a sorption column with reversibly dehydratable material into the rinsing container in order to heat the rinsing liquor and/or items to be washed.
As is well known, conventional dishwashers have a washing process whose programme sequence generally consists of at least one “Prewash” partial programme step, a “Clean” partial programme step, at least one “Intermediate Wash” partial programme step, a “Clear Wash” partial programme step and a “Drying” partial programme step. In order to increase the cleaning effect the rinsing liquor is in this case heated before or during a partial programme step. The rinsing liquor is normally heated by means of electric heating devices. Different drying systems are known for drying the items to be washed in a dishwasher.
A dishwasher of the type just mentioned is disclosed in DE 20 16 831, in which the air is conducted from the rinsing container via a sealable opening in the wall of the rinsing container on reversibly dehydratable material and from there via an opening to the outside. The desorption of the reversibly dehydratable material takes place during the non-operating phase of the dishwasher, the water vapour formed thereby being conducted to the outside via the opening. The dishwasher described is disadvantageous from the energy viewpoint because the regeneration of the reversibly dehydratable material takes place during a non-operating phase of the dishwasher, i.e. at a time when none of the partial programme steps already described is being carried out. A further disadvantage consists in the fact that the possibility of damage to the surrounding kitchen furniture cannot be ruled out because of the discharge of the water vapour formed during the regeneration of the reversibly dehydratable material to the outside. In this case the regeneration is associated with an additional energy requirement which is added to the energy required during the partial programme steps.
In order to minimise the energy expenditure when operating a dishwasher, DE 103 53 774.0 of the applicant discloses a dishwasher with a rinsing container and devices for washing dishes by means of rinsing liquor, which dishwasher has a sorption column connected in an air-conducting manner to the rinsing container and containing reversibly dehydratable material, wherein on the one hand the sorption column is used to dry the dishes and on the other hand the thermal energy used for desorption of the sorption column is at least partially used for heating the rinsing liquor and/or the dishes.
To solve this same problem DE 103 53 775.9 of the applicant proposes, for operating a dishwasher, to conduct air in the at least one “Drying” partial programme step from a rinsing container and/or from ambient air through a sorption column and into the rinsing container, the sorption column containing reversibly dehydratable material and moisture being extracted from the air during its passage.
Heating of the items to be processed is normally no longer necessary in the partial programme step preceding the “Drying” partial programme step due to the use of reversibly dehydratable material with a hygroscopic property, e.g. zeolith. This allows a considerable energy saving.
EP 0 358 279 B1 discloses a device for drying dishes in a domestic dishwasher in which the rinsing liquor is heated by a heater arranged outside the rinsing container, preferably an electric geyser, a largely closed drying system being provided here in which air circulates from the rinsing container via a drying device that can be regenerated by heating and from this device back into the rinsing container. Here the drying device consists of a drying container in thermal contact with the heater, which container is filled with a drying means adsorbing the moisture. Because the drying container is connected to the heater provided in any case for heating the rinsing liquor, the drying device is immediately operational after completion of the rinsing process. The drying means is in this case placed at least partially around the heating elements as a jacket so that the drying means can be heated and hence dried in the drying container during each heating process.
The drying container is designed as a double-wall hollow cylinder into which the drying material is introduced. The inlet and outlet opening for connection to the closed air system are arranged diagonally opposite one another. The disadvantage of this is that it gives rise to a relatively flow resistance, with the result that the fan provided for conveying the air flow must be operated at very high power. This has a negative effect in terms of noise development and energy consumption.
Because of the structural design of the sorption drier, which requires inhomogeneous introduction of heat into the drying material, the desorption is time consuming and may also lead to local overheating of the drying means and hence to its irreversible damage. The desorption is also difficult because the heater is arranged in the centre of the double-wall hollow cylinder and radial distribution of heat to the drying means close to the outer hollow cylinder wall is hardly possible because of the air flowing axially past it.